Thermal recording materials are formed by laminating a thermal recording layer and a protection layer sequentially on a support layer such as paper and a plastic film, and are widely used as, for example, facsimile, and print sheet.
The thermal recording layer and the protection layer of such a thermal recording material are formed from a resin material such as acrylic resin. For the resin material, for example, Patent Document 1 has proposed a core-shell type copolymer emulsion produced by copolymerizing 90 parts of methacrylamide and 10 parts of methacrylic acid in the presence of seed emulsion produced by 46 parts of acrylonitrile, 46 parts of butyl acrylate, 5 parts of 2-hydroxyethyl methacrylate, and 3 parts of methacrylic acid (Production Example C).
By using the thus produced copolymer emulsion as the thermal recording layer and the protection layer of the thermal recording material, a thermal recording material with excellent running stability (anti-sticking properties) and durability (heat resistance, plasticizer resistance, anti-blocking, water resistance, solvent resistance, oil resistance) can be produced.
For the methods for forming the thermal recording layer and the protection layer using the copolymer emulsion, for example, curtain coating is known: in curtain coating, a copolymer emulsion is allowed to fall in the form of curtain while a support layer is passed through the liquid.